1. FIELD
This invention relates generally to systems for preventing headlight glare from oncoming traffic on a divided highway, and more specifically to a glarefoil assembly in which light obstructing members are adjustable.
2. PRIOR ART
Blinding headlight glare has long been a problem for travellers on divided highways. Responsive to this problem, a number of attempts have been made to reduce the dangers inherent thereto. For example, shrubbery and other plants have been planted on islands or median barriers separating the divided lanes to block out glare from oncoming traffic. This attempt has been largely unsuccessful, however, due to the inordinate amount of time and effort necessarily expended in keeping the plants watered, trimmed and otherwise cared for. Also, a long wait is associated with initially growing the plants to an acceptable level and the crews responsible for the maintenance of the plants are subjected to substantial safety risks when working in the middle of a busy highway or interstate freeway.
Another attempt to reduce the glare associated with two-way traffic is the use of a solid screen made of aluminum or a similar rigid material and mounted to steel posts imbedded in the top of the median barrier. While effective in eliminating headlight glare, maintenance and cost considerations make this alternative undesirable. Screens of this sort often come loose from anchorings and supports as they are buffeted about by winds, many of which may be caused by passing traffic. Also, large aluminum screens which are torn or otherwise damaged, even when only minor damage is sustained, require replacement of the entire screen.
Such screens are further the object of mischief and vandalism in the form of thrown articles such as rocks, bottles and hardened refuse. This, of course, only adds to the problems associated with solid screens already mentioned. Another problem with rigid screens is that they can serve as a solid barrier for police, ambulances and other emergency vehicles. Thus, not only can critical delays be caused by these screens, but they can also become very expensive as they are cut through to allow passage of such vehicles in response to emergency situations.
Responsive to the problems encountered with the use of rigid screens, glarefoils, which are mounted individually on the top of median barriers, were created. These foils extend up to four feet above the median barrier and are constructed of polyethylene or a similar type of thermoplastic material. A great advantage is provided by these glarefoils in that they provide better cross-over access by emergency vehicles and also in that maintenance costs and problems are significantly lessened. Glarefoils are smaller, less costly and can be replaced much easier than the rigid solid screens mentioned above. Also, the flexibility of these glarefoils allows them to yield upon impact with objects such as those already described and then regain their normal shape and position.
Some disadvantages are experienced with glarefoils, however. The typical glarefoil is individually mounted directly to the top of the median barrier by several bolts. Because of this, the installation, removal and replacement of each glarefoil is time consuming and therefore costly. Further, the material of which these foils are constructed becomes brittle over time and thus they become prone to break off when exposed to extreme temperatures, ultraviolet radiation from the sun and constant buffetings by the wind and air currents from passing cars.
An improved glarefoil assembly is disclosed and claimed in applicant's U.S. Pat. No. 4,338,041 issued in 1982. This glarefoil provides improved materials which not only last longer than materials theretofore used, but which also have the capabilities of transmitting vibrational energy, caused by impact with moving objects or wind, from the point of impact on a glarefoil to a base runner. The base runner functions as a mounting plate for the individual glarefoil blades and is thus affixed to the top of the median barrier. Hence, when the glarefoils are buffeted by wind or impacted by an object, the resulting vibrational energy is transferred to the base runner, which, because it is attached to the median barriers at only three to five points, begins to vibrate. Vibrational energy transferred from other glarefoil blades counteract and dampen the vibration in the base runner, as do the fixed points of the base runner, with a net result of cancellation of much of the vibrational energy.
While the '041 patent has substantially furthered the art of glarefoils, a distinct limitation remains. Specifically, the '041 patent teaches a glarefoil member which is rigidly connected to the base runner in fixed angular orientation. Because the blades are spaced at fixed distances and angles, they are not adaptable for use with more than one road curvature. For example, if a set of glarefoil blades are oriented so as to prevent sight access on a straight road in optimum fashion, those same blades cannot be used to prevent sight access on a curved road because approaching cars in one of the lanes are allowed to see through the blades, thus defeating the purpose.
Such a limitation mandates that either the assembly only be used on one specific curvature of road or else that the glarefoil blades overlap each other in order to allow for placement on a variety of road curvatures. Overlap constitutes a significant waste of materials and manufacturing cost.
Furthermore, when the orientation of the glarefoil bladder is preset and nonadjustable, a given set of glarefoil blades can be used only on either the median strip between opposing lanes of traffic or on the exterior edge of a lane of traffic, but not on both, since the correct sight inhibiting orientation for the median strip is opposite that for the exterior edge.
Therefore, a legitimate need exists for a glarefoil assembly having the characteristics described in the 041 patent having the further feature of angularly adjustable glarefoil blades to allow for adaptability to a variety of road curvatures.
A more detailed description of the prior art has been catalogued and summarized in a publication of the Transportation Research Board of the National Research Counsel in cooperation with the Federal Highway Administration, entitled "Glare Screen Guidelines." This report is dated December 1979 and is available from the Transportation Research Board of the National Academy of Sciences, Washington, D.C.